MgO和SiO2烧结添加剂对陶瓷刚玉磨料性能的影响

以氧化镁和氧化硅为烧结添加剂，利用无压烧结工艺制备了陶瓷刚玉磨料。借助扫描电子显微镜和金刚石静压强度测定仪等测试设备，研究了氧化镁、氧化硅配比的变化对陶瓷刚玉磨料显微结构、力学性能和烧结温度的影响。实验结果表明，提高添加剂中氧化镁成分的相对含量，晶粒呈明显各向异性生长：随着添加剂中氧化镁含量的相对增加，磨料单颗粒抗压强度先增加后降低；磨料的烧成温度随添加剂中氧化镁含量的增加逐渐升高。     

MgO—CeO2烧结助剂对常压烧氮化硅陶瓷致密化和性能的影响

系统研究了ＭｇＯ－ＣｅＯ２烧结助剂对常压烧结氮化硅陶瓷致密化过程及其性能的影响，发现ＭｇＯ－ＣｅＯ２是一咱非常有效的烧结助剂，其致密化效果比单独用ＭｇＯ或ＣｅＯ２要好得多，常压烧结的Ｓ３Ｎ４－ＭｇＯ－ＣｅＯ２陶瓷，相对密度为９８．５％，室温强度可达９４８ＭＰａ。     

掺杂TEOS的YAG透明陶瓷相转变、烧结及微观组织

分别添加0.3%～3.0%(质量分数)的正硅酸乙酯(TEOS)为烧结助剂,利用液相烧结合成钇铝石榴石(Y3Al5O12,YAG)透明陶瓷。结果表明:液相生成是一种动态过程,最低形成温度约为1400℃。烧结体相对密度随着烧结温度的升高而明显增大,且烧结助剂对致密化过程的促进作用与其含量有关。当w(TEOS)≤0.5%时,TEOS能够更明显地促进烧结,TEOS含量对真空烧结后烧结体内残留硅酸盐相的数量、分布和显微结构产生很大的影响。当w(TEOS)≤0.5%时,Y2Si2O7与Al2O3·SiO2(MUL)固溶于YAG晶粒内,晶界处没有残留第二相;当w(TEOS)为2%和3%时,过量的Y2Si2O7与MUL在晶界析出而成为散射源,严重损害陶瓷的光学性能。     

无压烧结制备YAG多孔陶瓷的工艺及性能

为了能够利用YAG优异的性能开发出更多的功能材料,通过调整无压烧结技术工艺参数成功制备YAG多孔陶瓷材料。结果表明:1500℃烧结的YAG多孔陶瓷的气孔率与1550℃烧结的陶瓷相近,但是1550℃制备的陶瓷具有较多烧结颈使抗压强度较高。保温2 h的样品与保温1 h的样品进行对比表明,保温2 h样品包裹气泡长大使气孔率高,液相较多颗粒联接牢固使抗压强度高。升温速度为5℃/min制备的陶瓷比升温方式10℃/min制备的陶瓷气孔率和抗压强度都高。在800℃排碳所制备的样品的气孔率和抗压强度都比1000℃排碳的高。通过分析工艺参数与性能之间的内在联系,得出烧结温度为1550℃,保温2 h,升温速度为5℃/min,800℃排碳时间1 h制备的YAG多孔陶瓷材料较为适合,其材料气孔率为59.4%,抗压强度为8.55 MPa。     

改良固相法制备透明YAG陶瓷的研究

以高纯氧化铝(Al2O3)、氧化钇(Y2O3)为原料,使用卧式搅拌磨,系统研究了一种制备YAG粉体的改良固相法工艺。该工艺利用高达2000r/min的转速以及直径0.5mm的高纯氧化铝球球磨介质实现了Al2O3、Y2O3粉体亚微米级的均匀混合,可在1350℃实现两种粉体的固相反应,并完全转化为纯YAG粉体,大幅度地降低了YAG的转相温度。作者还初步研究了该粉体的烧结性能,成功制得了透明的YAG陶瓷。     

烧结助剂对Salon常压烧结的影响

研究了以Y2O3和Y2O3＋La2O3为烧结助剂的Sialon陶瓷的常烧结过程及其相结构。结果表明：添加6％Y2O3在1750℃常压烧结1h可获得相对密度大于99％的Sialon陶瓷;La2O3可部分或大部分取代Y2O3,混合烧结助剂的最佳烧结温度（1800℃）略高于单纯以Y2O3为烧结助剂的最佳烧结温度（1750℃）。加入La抑制了α′相和YAG相的生成,选择合适的工艺条件,可制得α′ β′复相陶瓷。探讨了用Col-Gel化学法混料替机械法混料的可能性,由于γ－Al2O3转变成α－Al2O3等原因,化学混料法的效果不如机械法。     

烧结助剂对HfB2-SiC基超高温陶瓷组织和性能的影响研究

采用热压烧结工艺制备出HfB2—20％SiC（HS）、HfB2-20％SIC-5％Si3N4（HSS）和HfB2—20％SIC-5％AIN（HSA）（体积分数，下同）3种超高温陶瓷基复合材料，对材料进行了微结构表征和力学性能测试，并对Si3N4、AIN烧结助剂的作用机理进行了初步分析。结果表明，与HfB2—20％SIC相比，Si3N4和AIN烧结助剂的引入使材料的烧结温度从2200℃降低到1850℃，相对密度从95％提高到99％左右。材料的平均晶粒尺寸显著降低，形成了相应的晶粒边界相。力学性能测试结果表明，HfB2—20％SiC-5％Si3N4和HfB2—20％SiC-5％AIN的抗弯强度和断裂韧性均比HfB2—20％SiC获得一定程度的提高。烧结助剂的引入使SiC／HfB2超高温陶瓷材料的断裂模式从单纯的穿晶断裂转变为穿晶／沿晶混合的断裂模式。     

烧结工艺对纳米WC/MgO复合材料性能的影响

利用高能球磨法和放电等离子烧结技术制备了纳米WC/MgO复合材料,研究了烧结温度和烧结压力对WC-8wt%MgO复合材料密度、硬度和断裂韧性的影响.结果表明,烧结温度过低,试样的致密度差;烧结温度过高,晶粒快速长大,使得复合材料性能降低;烧结压力越大,复合材料的致密度越高,硬度和断裂韧性越好.最佳烧结工艺是烧结温度1650℃,烧结压力70 MPa,获得了该复合块体材料的最佳性能组合.     

MgO含量对低硅烧结成矿性能的影响

利用实验室烧结杯实验,研究了MgO含量对低硅烧结的影响,控制烧结矿碱度为1.9,配碳量为4.5%,通过利用白云石调节烧结混合料中的MgO含量,并对烧结成矿进行冶金性能分析。试验结果表明:MgO含量由1.2%升高到1.6%时,烧结矿的强度得到改善,MgO含量由2.0%升高到2.8%时,烧结矿的强度逐渐变差;随着烧结矿MgO含量的升高,烧结矿的低温还原粉化性能和还原性能逐渐变差,荷重软化开始温度和终了温度升高,软化区间变宽。因此,在低硅烧结工艺中应尽量降低烧结混合料的MgO含量。     

Fabrication of Nd:YAG transparent ceramics with both TEOS and MgO additives

Neodymium doped YAG transparent ceramics were fabricated by vacuum reactive sintering method using commercial α-Al₂O₃, Y₂O₃ and Nd₂O₃ powders as the starting materials with both tetraethyl orthosilicate (TEOS) and MgO as sintering aids. The morphologies and microstructure of the powders and Nd:YAG transparent ceramics were investigated. Fully dense Nd:YAG ceramics with average grain size of ∼10 μm were obtained by vacuum sintering at 1780 °C for 8 h. No pores and grain-boundary phases were observed. The in-line transmittance of the ceramic was 83.8% at 1064 nm.     

Fabrication of transparent YAG ceramics by traditional solid-state-reaction method

Transparent polycrystalline YAG ceramics were fabricated by solid-state reaction method using commercial ultrafine yttria andα-Al2O3 powders.The starting materials were milled and calcined at 1 400℃,and sintered into transparent YAG ceramics at 1 750℃in the vacuum for 4 h.Neither the starting materials as-milled or those calcined into YAG phase at 1 500℃can be sintered into transparent ceramics.Wide grain boundaries emerge in the YAG ceramics sintered at 1 850℃for 4 h,at the edge of which YAG phases decompose into perovskite YAlO3(YAP)andα-Al2O3.     

Fabrication and laser output of transparent Nd:YAG ceramics from microwave synthesized precursors

We report the laser output of transparent Nd:YAG(Nd:Y3Al5O12) ceramics fabricated from Nd:YAG precursors through the microwave-assisted homogenous precipitation(MAHP) method.Pure phase and uniform Nd:YAG nano-powders with average sizes less than 100 nm were obtained by heating treatment of the Nd:YAG precursor particles aged for 6 d in vessel with humidity of 30%-50% at 25°C.Transparent Nd:YAG ceramic pellets were obtained by vacuum sintering at 1730°C for 10 h.Laser output(305 mW) with a slope efficiency o...     

均相沉淀法制备YAG球形粉体及透明陶瓷

以Y(NO3)3.6H2O和Al(NO3)3·9H2O为原料,尿素为沉淀剂,采用均相沉淀法合成了成分为5[Al(OH)CO3]·3[Y(OH)CO3]的钇铝石榴石(YAG)先驱体粉末。在沉淀过程中通过控制硫酸根离子的含量可以避免晶核生长时的方向性,有效防止了纳米颗粒硬团聚的形成,先驱体颗粒逐渐球化。经1 100℃煅烧分解,获得平均尺寸为200~400 nm、低团聚的高纯YAG球形粉体。该粉体经模压成型、1 700℃真空烧结,得到晶粒分布均匀、完全透明的YAG陶瓷。     

Preparation of transparent yttrium aluminum garnet ceramics by relatively low temperature solid-state reaction

1　INTRODUCTIONYttriumaluminum garnet(YAG )isakindofcomplexoxideresultedfromthereactionofY2 O3andAl2 O3.ItschemicalformulaisY3Al5O12 .Ithasagarnetcrystalstructureandbelongstohexagonalsys tem .YAGceramicsholdpromiseforcertainopticalapplicationssuchashightemperaturewindowsusedtodetectinfraredwavesordevicesusedtorecordnu clearradiation .Becauseofitsthermalstability ,highhardness,physicalandchemicalstability ,andexcel lenttransparencyinawidewavelengthregionfromvisiblelighttoinfraredlight…     

氧化镁陶瓷抗热震性能

以氧化镁为原料并添加稀土氧化物、CaO、V_2O_5、ZrO_2和Al_2O_3等烧结助剂,采用不同温度煅烧粉体,造粒、成型和烧结后,制备了致密的氧化镁陶瓷试样.随后,将加热的试样在水中急冷,经过不同次数后,观察样片表面开裂的情况.通过对样片密度、气孔率和硬度的测定,以及对试验材料显微结构的观察,分析了烧结助剂、粉体制备工艺和烧结工艺对氧化镁陶瓷抗热震性能的影响.     

CaF2助剂放电等离子烧结透明AIN陶瓷的微观结构和光学性能

采用放电等离子烧结技术，添加质量分数为3％的CaF2作为烧结助剂，制备了透明氮化铝（AIN）陶瓷。样品在烧结温度1800℃，30MPa压力下保温15min，达到了99．5％的相对密度和52．7％的最大透过率。SEM、XRD、TEM和EDX结果表明，烧结体具有很高的致密度、纯度，良好的晶粒形貌和微观晶体结构，晶界和三角晶界处观察不到第二相的存在。CaF2的添加引入液相烧结，促进AIN晶粒的生长和烧结体的致密化，并且与AIN颗粒反应生成的氟化物和Ca-Al-O化合物能够从烧结体中逸出，进一步净化烧结体，是制备透明AIN陶瓷的有效助剂。放电等离子烧结技术具有烧结快速、烧结体致密度高的特点，是制备透明AIN陶瓷的有效方法。     

Fabrication and optical properties of a highly transparent Nd：YAG ceramic

A neodymium doped yttrium aluminum garnet (Nd:YAG) transparent ceramic was fabricated by a solid state reaction method using commercial α-Al₂O₃, Y₂O₃, and Nd₂O₃ powders as starting materials and tetraethyl orthosilicate (TEOS) as sintering aid. The morphology and microstructure of the nanopowders and the Nd:YAG transparent ceramic were investigated. The fully dense Nd:YAG ceramic with an average grain size of ∼20 μm was obtained by vacuum sintering at 1720°C for 12 h. Few pores and grain-boundary phases were observed. The in-line transmittance of the ceramic was 81.5% at 1064 nm.     

Pulsed laser deposition of transparent ZnO/MgO multilayers

We report on the structural, optical and electrical properties of ZnO/MgO multilayers grown by pulsed laser deposition technique. The film thickness of ZnO sublayer (t_ZnO) was found to have great impact on the properties of ZnO/MgO multilayers. Investigations reveal the structural phase transition from wurtzite phase to cubic phase with corresponding decrease in ZnO thickness. The optical transmittance of the multilayers is over 80% in the visible region and there is a gradual shift of absorption edge towards a longer wavelength with corresponding increase in ZnO sublayer thickness. Two absorption bands at around 400 nm and 270 nm were observed in the transmission spectra of ZnO/MgO multilayers for similar ZnO and MgO layer thickness, which has been ascribed to phase separation to hexagonal and cubic phases. The calculated optical band gap E_g shows a widening from 3.51 eV to 6.23 eV with corresponding decrease in ZnO sublayer thickness from 100 nm to 23 nm, which in turn leads to an increase in resistivity in ZnO/MgO multilayers. These results provide important information for the design and modeling of ZnO/MgO optoelectronic devices due to their adjustable bandgap energies.     

Yb:YAG与Nd:YAG纳米晶的制备及性能

通过超声-微波辅助醇盐水解沉淀法合成了Yb:YAG与Nd:YAG纳米晶。研究了微波辐射功率、微波辐射时间及煅烧温度对产物的影响。采用X-射线粉末衍射(XRD)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)及光致发光谱(PL)等对Yb:YAG与Nd:YAG纳米晶进行表征。结果表明,在微波辐射功率385 W、微波辐射时间30 min、煅烧温度1100 C条件下,可以获得纯相Yb:YAG与Nd:YAG纳米晶。当煅烧温度为1100 C时,Yb:YAG与Nd:YAG纳米晶的合作发光强度均达到最大值。